1. Field of the Invention
The present invention relates to a welding method and welding equipment for welding inner cylinders to an outer cylinder. It is applicable to, for example, the fabrication of a combustion liner.
2. Description of the Related Art
By way of example, a liner for a combustor in a gas turbine is fabricated by welding a liner body 1 forming an outer cylinder and rings 2 forming inner cylinders as illustrated in FIGS. 4 and 5.
The combustion liner 5 of the specified type is fabricated in such a way that the rings 2 are arranged at predetermined positions in the liner body 1, and that the liner body 1 and the rings 2 are tacked by spot welding and are thereafter brazed.
In the spot welding and the brazing, a sufficient bond strength cannot be attained unless the spacing between the inner peripheral surface of the liner body 1 and the outer peripheral surface of each of the rings 2 is within a predetermined value. Especially in the brazing operation, the brazing itself cannot be effected unless the spacing is within 0.1 mm.
For these reasons, the liner body 1 and the rings 2 have heretofore been subjected to precision machining in order that the inner peripheral surface of the former and the outer peripheral surfaces of the latter may define the appropriate spacings.
Since the precision-machined liner body and rings are used for enhancing the reliability of the welding, the prior art has had the problem that the cost of fabrication is high.